Recombinant Delftia acidovorans UPF0761 membrane protein Daci_4966 (Daci_4966)

What is Delftia acidovorans UPF0761 membrane protein Daci_4966?

Daci_4966 is a membrane protein encoded by the Delftia acidovorans genome (strain DSM 14801 / SPH-1) with UniProt accession number A9BMQ0. It belongs to the UPF0761 protein family and consists of 417 amino acids forming a complete membrane-spanning structure. The protein is characterized by multiple transmembrane domains that anchor it within the bacterial cell membrane . Delftia acidovorans is primarily an environmental organism rarely associated with clinical significance, though it has been documented in some rare infections .

How does Daci_4966 compare to other membrane proteins in Delftia acidovorans?

While Daci_4966 is characterized as a UPF0761 family membrane protein, Delftia acidovorans also expresses other significant membrane proteins, most notably Omp32, which is the major outer membrane protein of the bacterium. Unlike Daci_4966, Omp32 has been extensively characterized structurally and functionally as an anion-selective porin with a 16-stranded beta-barrel structure. Omp32 demonstrates specific substrate binding capabilities, particularly for malate, which reflects the physiological adaptation of the organism to organic acids . Comparative analysis between these membrane proteins can provide insights into the diverse functional roles of membrane proteins within the same organism.

What are the optimal storage conditions for recombinant Daci_4966?

Recombinant Daci_4966 should be stored under the following conditions for maximum stability and activity:

It's important to note that repeated freezing and thawing cycles should be avoided as they can significantly degrade protein quality. Instead, prepare small working aliquots for routine experiments . For applications requiring extended stability, storage at -80°C is preferable over -20°C.

How can I measure the diffusion rate of Daci_4966 in membrane systems?

The lateral diffusion rates of membrane proteins like Daci_4966 can be measured using fluorescence-based techniques:

• Fluorescence Recovery After Photobleaching (FRAP): This method involves:

  • Marking Daci_4966 with a specific fluorescent group (either using a fluorescent ligand like an antibody or expressing the protein fused to GFP)

  • Bleaching the fluorescent group in a small area using a laser beam

  • Measuring the time taken for adjacent unbleached protein molecules to diffuse into the bleached area

  • Calculating the diffusion coefficient from the recovery curve

• Fluorescence Loss in Photobleaching (FLIP): This complementary technique involves:

  • Continuously irradiating a small area with a laser beam

  • Monitoring the gradual depletion of fluorescently labeled molecules from surrounding membrane areas

  • Analyzing the rate of fluorescence loss to determine diffusion properties

These techniques can provide valuable information about Daci_4966's mobility within the membrane and potential interactions with other membrane components .

What expression systems are recommended for producing recombinant Daci_4966?

• Prokaryotic systems (E. coli):

  • Advantages: High yield, cost-effective, rapid growth

  • Limitations: Potential issues with proper folding of complex membrane proteins

  • Recommended strains: C41(DE3) or C43(DE3) that are engineered for membrane protein expression

• Eukaryotic systems:

  • Insect cells (Sf9, Hi5): Better for complex membrane proteins requiring post-translational modifications

  • Yeast (Pichia pastoris): Combines high yields with eukaryotic processing capabilities

• Cell-free systems:

  • Useful for toxic membrane proteins

  • Allows direct incorporation into nanodiscs or liposomes

The optimal expression system should be determined through small-scale trials comparing protein yield, folding quality, and functional activity.

What techniques are most effective for determining the structure of Daci_4966?

For structural determination of membrane proteins like Daci_4966, multiple complementary approaches should be considered:

• X-ray Crystallography: Requires:

  • Purification in detergent micelles or lipidic cubic phase

  • Screening of numerous crystallization conditions

  • This approach was successful for the related Omp32 protein from Delftia acidovorans, yielding high-resolution structures (1.5 Å and 1.45 Å)

• Cryo-Electron Microscopy (Cryo-EM):

  • Increasingly popular for membrane proteins

  • May not require crystallization

  • Can capture multiple conformational states

  • Particularly useful if Daci_4966 forms larger complexes

• NMR Spectroscopy:

  • Suitable for smaller membrane proteins or specific domains

  • Can provide dynamics information not available from static structures

  • Typically requires isotopic labeling (15N, 13C)

• Computational Approaches:

  • Homology modeling based on related structures

  • Molecular dynamics simulations to study conformational changes

  • Similar to the 7-ns unbiased molecular dynamics simulation performed for Omp32

The choice of method should be guided by the specific research questions and available resources.

How can I predict the membrane topology of Daci_4966?

Predicting the membrane topology of Daci_4966 requires a multi-faceted approach:

• Computational prediction tools:

  • TMHMM, HMMTOP, or TOPCONS for transmembrane helix prediction

  • PROFtmb for beta-barrel prediction

  • SignalP for signal peptide identification

• Experimental validation:

  • Cysteine scanning mutagenesis with accessibility assays

  • Protease protection assays to identify exposed regions

  • Reporter fusion constructs (e.g., PhoA or GFP) to determine orientation

• Combined approach:

  • Start with computational predictions

  • Verify key topological features experimentally

  • Refine models based on experimental data

This systematic approach helps establish a reliable topology model that can guide further structural and functional studies of Daci_4966.

What are the predicted functional roles of Daci_4966 based on sequence analysis?

While specific functions of Daci_4966 have not been definitively established in the available literature, sequence analysis and comparison with related proteins suggest potential roles:

• Membrane transport: The multi-transmembrane domain structure is characteristic of proteins involved in small molecule transport across membranes.

• Signaling function: Some UPF (Uncharacterized Protein Family) members participate in signal transduction across membranes.

• Structural role: It may contribute to membrane integrity or organization within Delftia acidovorans.

• Stress response: Environmental bacteria often utilize membrane proteins as part of adaptation mechanisms to changing conditions.

To confirm these predicted functions, targeted experimental approaches would be required, including gene knockout studies, substrate transport assays, and protein-protein interaction analyses.

How can I investigate potential ligand interactions with Daci_4966?

To investigate ligand interactions with Daci_4966, consider these methodological approaches:

• Binding assays:

  • Isothermal Titration Calorimetry (ITC) to measure binding thermodynamics

  • Surface Plasmon Resonance (SPR) for real-time binding kinetics

  • Microscale Thermophoresis (MST) for interactions in solution

• Structural approaches:

  • Co-crystallization with potential ligands (similar to the approach used for Omp32 with malate)

  • NMR chemical shift perturbation experiments

  • Cryo-EM with bound ligands

• Functional assays:

  • Electrophysiology measurements in planar lipid bilayers (as used for Omp32)

  • Substrate transport assays using proteoliposomes

  • Fluorescence-based flux assays with reconstituted protein

• Computational methods:

  • Molecular docking to predict binding sites

  • Molecular dynamics simulations to assess ligand recognition and binding stability

A comprehensive investigation would typically combine multiple approaches to build a complete picture of ligand interactions.

How can Daci_4966 be incorporated into membrane model systems for functional studies?

Incorporating Daci_4966 into membrane model systems is critical for functional characterization. Several approaches are available:

• Proteoliposomes:

  • Purified Daci_4966 can be reconstituted into liposomes of defined lipid composition

  • Method: Detergent-mediated reconstitution followed by detergent removal via dialysis or bio-beads

  • Applications: Transport assays, ligand binding studies, structural analysis

• Planar lipid bilayers:

  • Creates accessible membranes for electrical measurements

  • Method: Painting or folding techniques to form bilayers, followed by protein incorporation

  • Applications: Electrophysiology to measure channel or transport properties (similar to conductance measurements performed with Omp32)

• Nanodiscs:

  • Disc-shaped lipid bilayers stabilized by membrane scaffold proteins

  • Method: Co-assembly of purified Daci_4966, lipids, and scaffold proteins

  • Applications: Structural studies, binding assays, single-molecule measurements

• Cell-based systems:

  • Expression in model cell lines lacking endogenous transport systems

  • Method: Transfection or viral transduction of Daci_4966 expression constructs

  • Applications: Functional assays in cellular context, localization studies

The choice of system depends on the specific research questions and experimental techniques to be employed.

What insights can molecular dynamics simulations provide about Daci_4966 function?

Molecular dynamics (MD) simulations can provide valuable insights into Daci_4966 function that may be difficult to obtain experimentally:

• Structural dynamics:

  • Conformational flexibility and transitions between states

  • Local motions of functional importance

  • Similar to the 7-ns unbiased MD simulation performed for Omp32

• Interaction with lipid environment:

  • Specific lipid-protein interactions

  • Hydrophobic matching with the membrane

  • Influence of membrane composition on protein behavior

• Substrate transport mechanisms:

  • Pathways for substrate entry and exit

  • Energy barriers along transport pathways

  • Key residues involved in substrate recognition and translocation

  • Similar to how MD trajectories showed malate ion capture and translocation for Omp32

• Water and ion permeation:

  • Formation of water wires through the protein

  • Ion selectivity mechanisms

  • Gating dynamics

To perform meaningful MD simulations of Daci_4966, the protein should be embedded in a lipid bilayer with appropriate composition, solvated, and simulated for adequate timescales (typically microseconds) to observe relevant functional events.

What strategies can address poor expression or folding of recombinant Daci_4966?

Membrane proteins like Daci_4966 often present challenges in expression and folding. Here are systematic approaches to address common issues:

• Poor expression yield:

  • Optimize codon usage for the expression host

  • Test different promoter strengths

  • Vary induction conditions (temperature, inducer concentration, timing)

  • Consider specialized expression strains designed for membrane proteins

  • Try fusion tags that enhance expression (e.g., MBP, SUMO)

• Misfolding and aggregation:

  • Reduce expression rate (lower temperature, weaker promoter)

  • Co-express with chaperones

  • Use mild detergents for extraction and purification

  • Include stabilizing additives (specific lipids, ligands)

• Protein degradation:

  • Add protease inhibitors during purification

  • Consider the ER-associated degradation pathway's role in quality control of membrane proteins

  • Use protease-deficient expression strains

• Purification challenges:

  • Screen multiple detergents for extraction efficiency

  • Optimize detergent:protein ratios

  • Consider native nanodiscs or SMALPs for extraction

  • Test different chromatography approaches

Systematic optimization using small-scale expression tests can help identify the most effective conditions before scaling up.

How can I assess the proper folding and functionality of purified Daci_4966?

Verifying proper folding and functionality of purified Daci_4966 is essential before proceeding with detailed studies:

A well-folded membrane protein typically demonstrates characteristic secondary structure content, monodisperse behavior in solution, and functional activity when reconstituted into membrane systems.

How does the membrane environment influence Daci_4966 structure and function?

The lipid environment can significantly impact membrane protein behavior through various mechanisms:

• Hydrophobic matching:

  • The hydrophobic thickness of the lipid bilayer must match the hydrophobic region of Daci_4966

  • Mismatch can lead to protein tilting, distortion, or aggregation

• Specific lipid interactions:

  • Certain lipids may bind to specific sites on Daci_4966

  • These interactions can stabilize particular conformations

  • They may be essential for function, similar to how membrane proteins adapt to their environment

• Membrane fluidity effects:

  • Lateral diffusion rates of Daci_4966 are influenced by membrane fluidity

  • Different lipid compositions alter protein dynamics and potentially function

  • Techniques like FRAP can measure these effects

• Experimental approaches:

  • Systematic testing of different lipid compositions in reconstitution experiments

  • Native mass spectrometry to identify bound lipids

  • Molecular dynamics simulations to observe lipid-protein interactions

Understanding these interactions is crucial for accurately characterizing Daci_4966's native behavior and for optimizing experimental conditions.

What is the role of Daci_4966 in the context of bacterial physiology?

While specific information about Daci_4966's physiological role is limited in the available literature, we can make informed hypotheses based on knowledge of bacterial membrane proteins and Delftia acidovorans biology:

• Environmental adaptation:

  • Delftia acidovorans is known to inhabit diverse environments, from soil to clinical settings

  • Membrane proteins often play key roles in adapting to changing conditions

  • Daci_4966 may facilitate survival in specific niches

• Metabolic functions:

  • Related membrane proteins in Delftia acidovorans (e.g., Omp32) show specificity for organic acids

  • Daci_4966 might participate in nutrient acquisition or metabolite export

• Experimental approaches to determine physiological role:

  • Gene knockout or knockdown studies with phenotypic analysis

  • Expression profiling under different growth conditions

  • Protein-protein interaction studies to identify functional partners

  • Metabolomic analysis of wildtype vs. Daci_4966-deficient strains

• Comparative genomics:

  • Identification of Daci_4966 homologs in related species

  • Correlation of protein presence with specific metabolic capabilities

  • Evolutionary analysis to trace functional adaptation

These investigations would provide valuable context for understanding Daci_4966's contribution to Delftia acidovorans biology.